To help Riki Naoe recover from the tragic loss of his parents, four kids recruit him into their group called the "Little Busters." Still best friends in high school, their visions as heroes of justice has faded, but they will do anything for each other. Riki is on two special missions. The obvious one is recruiting new members so they can form a baseball team, and preferably females as the current guy/girl ratio is an inconvenient 4 to 1. But the second one is strange, as Riki and Rin, the group's only girl, are receiving odd messages delivered by cats concerning the existence of a secret world.